Visual assessment of the Ki67 index in breast cancer using the global scoring

Introduction. Neoadjuvant therapy (NAT) provides an in vivo assessment of primary tumor sensitivity to systemic therapy. However, the data on Ki67 clinical significance as a prognostic factor for the effectiveness of chemotherapy in breast cancer (BC) cause controversy. The International Ki67 Interpretation Workgroup for Breast Cancer (IKWG) meeting held in October 2019, recommended developing a standardized methodology for visual global scoring, which is proposed to be used in clinical practice. The aim of the study was to assess the clinical significance of Ki67 using visual global scoring in BC. Materials and methods. The study included 32 patients with proven BC that received preoperative neoadjuvant therapy. We studied paraffin histological blocks, analyzed the Ki67 expression over time in patients with residual tumors, and assessed the correlations of clinical and morphological signs before treatment. Ki67 was determined as the overall average with global scoring. The Ki67 scoring app for smartphones was used as an auxiliary tool to increase the accuracy. Results. The median value of the Ki67 index before NAT was 75.0% (34.8–85.0) and after the therapy it was 1.0% (0.0–6.2) [p<0.0001]. The Ki67 value was significantly lower (p=0.0077) [36% (30–75)] in the presence of residual tumor compared to that in patients without it [85% (78.8–90)]. Conclusion. The Ki67 index before NAT is a strongly prognostic factor of its effectiveness. The research of the Ki67 marker for concomitant diagnosis, which showed prognostic Ki67 role, can be considered as a correct diagnostic vector, only if strict analytical validity is observed. Keywords: Ki67, breast cancer, neoadjuvant therapy, global scoring, IKWG, Ki67 scoring app